Porous pipe and apparatus and method of producing the same

ABSTRACT

There are provided a porous pipe excellent in an absorbing and draining function, a producing apparatus capable of producing a porous pipe at high speed and low cost and a method of producing a porous pipe. The porous pipe is a pipe mainly constituted by spirally winding a tape and is constituted such that there is arranged a hole forming portion  13  for forming a recess or a notch or a hole at a tape  2  molded by a tape molding portion  11  between the tape molding portion  11  and a pipe forming portion  12  and the tape  2  is molded, a hole  6  is formed and a pipe  1  is formed continuously. The hole  6  is formed into a predetermined shape by elongating the hole  6  from a side of the pipe forming portion  12 . According to the pipe  1  formed thereby, a peripheral wall portion of the hole  6  is gradually thin-walled toward an outer peripheral face of the hole.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to a porous pipe preferably used as, for example, a drainpipe for a culvert and an apparatus of producing the same and a method of producing the same.

[0003] 2. Description of the Related Art

[0004] As a method of forming a number of holes at a pipe wall made of synthetic resin, conventionally, there are used a method of perforating at a nonporous pipe by moving a drill in a forward and rearward direction and a method of previously producing a perforated tape and forming a pipe by spirally winding the tape at a separate step.

[0005]FIG. 13 shows an example of a conventional porous pipe formed by spirally winding a tape. In the drawing, notation 31 designates a flat tape made of resin previously aligned with a number of holes 32, 32 . . . in a longitudinal direction and notation 33 designates a corrugated tape having a section in a shape of a channel-like groove and integrally provided with connection pieces 34 directed outwardly at both front ends in a cross direction thereof. Further, by overlapping the flat tape 31 and the corrugated tape 33 such that the two end edges of the flat tape 31 are overlapped to the connection pieces 34 of the corrugated tape 33 and winding the both members spirally while melting together or adhering together the both members, there is formed a corrugated pipe having the holes 32, 32 . . . at valley portions of an outer periphery thereof.

[0006]FIG. 14 shows to enlarge a portion of the hole of the porous pipe formed by the conventional method in which the hole 32 is formed substantially orthogonally to a pipe wall 35 and an inner peripheral face of the hole 32 and a surface of the pipe wall 35 are constituted to be substantially orthogonal to each other. An arrow mark of the drawing designates flow of water flowing into the hole 32.

[0007] In the above-described conventional methods, according to the former method of perforating the nonporous pipe hole by hole by the drill, there is a drawback that there is a limit in speed of moving the drill and perforating speed, that is, production speed of a porous pipe cannot be increased. Further, there poses a problem of poor operational environment such as producing drilling chips or emitting noise. In addition, there also poses a problem that the pipe wall is warped in drilling and therefore, strength of the pipe is reduced.

[0008] Meanwhile, according to the latter method of forming holes in producing the tape, there is needed a special apparatus capable of forming holes in forming such a tape. Further, production of the tape and forming of the pipe are carried out by separate steps and therefore, there poses a problem that the number of steps is increased and production cost is increased. Further, there is also needed a place for storing the tape before being employed to a pipe forming machine and control therefor is also needed.

[0009] In addition, according to the corrugated porous pipe formed by being wound spirally, as shown by FIG. 13, the end edge of the perforated tape 31 is made to overlap the tape 33 on the other side and melted together or adhered together and therefore, there is a drawback that a portion of the perforated tape 31 is restricted by an amount of the overlapped portion, the porosity cannot be increased and an absorbing or draining function is deteriorated by that amount.

[0010] Further, as shown by FIG. 14, according to the conventional porous pipe, the surface of the pipe wall 35 at the surrounding of the hole 32 is made substantially orthogonal to a peripheral wall of the hole 32 and therefore, when the porous pipe is used for a drain pipe of a culvert or the like, there is a case in which water does not necessarily flow smoothly to the hole 32 and the absorbing function is not sufficient.

OBJECT OF THE INVENTION

[0011] That is, it is an object of the invention to provide a porous pipe excellent in an absorbing and draining function, an apparatus of producing a porous pipe and a method of producing a porous pipe capable of producing a porous pipe at high speed and low cost by resolving drawbacks of the conventional porous pipe and the method of producing the same.

[0012] It is other object of the invention to provide a porous pipe in which a pipe wall at a surrounding of a hole is gradually thin-walled toward the hole and a surface of the surrounding is gradually inclined to thereby provide a porous pipe having a feeding and draining function more excellent than that of a conventional porous pipe in which a pipe wall is substantially orthogonal to a peripheral wall of a hole.

[0013] It is other object of the invention to provide a porous pipe in which in a corrugated pipe constituted by spirally winding a tape, a hole is provided at a center piece portion of the tape having a substantially channel-like section and by melting or adhering together a preceding tape and a succeeding tape at an outer side portion of the center piece in the width direction, it is not necessary to provide an overlapping margin for melting together or adhering together the tapes at the center piece. Therefore, the diameter of the hole can be enlarged to a full width of the center piece and a porous pipe having a large porosity and excellent in a feeding and draining function is provided.

[0014] It is still other object of the invention to provide an apparatus and a method of producing a porous pipe excellent in a production efficiency by directly employing a tape molded by a tape molding portion to a pipe forming portion as it is, continuously molding the tape and forming the pipe and forming a hole between the tape molding portion and the pipe forming portion. That is, according to the invention, there is provided an apparatus and a method of producing a porous pipe more excellent in the production efficiency than a constitution of forming a pipe by newly employing a temporarily perforated tape to a pipe forming machine or the like, further, with no necessity of storing the tape before employing the tape to the pipe forming machine or the like and dispensing with a space for storing the tape and control of a semiproduct thereof.

[0015] It is still other object of the invention to provide an apparatus and a method of producing a porous pipe without producing drilling chips, with no concern of emitting noise as in a drill and without deteriorating an operational environment since a hole can be formed only by making a recess or a notch to a tape in a state near to a molten state immediately after coming out from a tape forming machine.

[0016] It is still other object of the invention to enable high speed formation because a hole can continuously be formed at a moving tape and dispensing with a special apparatus for pulling the tape by providing a tension for elongating the tape at that occasion by utilizing driving force of a pipe forming portion.

[0017] It is still other object of the invention to provide an apparatus and a method of producing a porous pipe capable of easily forming a hole also at a side wall portion of a valley portion in a spiral corrugated pipe since the hole is formed at a stage of a tape before forming the pipe, further, preventing residual stress from causing even when the pipe is formed by melting together of a preceding side and a succeeding side of the same tape even by perforating at the melted portion. Therefore, according to the invention, there can be provided a pipe having a very large porosity formed with holes over a total face thereof in a longitudinal direction without being restricted in a position of forming the hole such as a mountain portion or a valley portion of the corrugated pipe.

[0018] It is still other object of the invention to be able to maintain an absorbing and draining function over a long period of time by perforating also at a side wall and a top portion of the pipe although the absorbing and draining function is deteriorated particularly in a drain pipe buried in a culvert or underground since sediments or the like are liable to store at the valley portion to thereby cause clogging.

[0019] An object of the invention other than the above-described and interest provided thereby can clearly be understood by the following description explained in reference to embodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In the drawings showing embodiments of the invention:

[0021]FIG. 1 is a partially sectional vertical view of a porous pipe according to an embodiment of the invention;

[0022]FIG. 2 is an outline total view of an apparatus of producing the same porous pipe;

[0023]FIG. 3 is a plane view of a portion of a tape after enlarging holes thereof;

[0024]FIG. 4 is a sectional view enlarging an essential portion of the tape taken along a line A-A of FIG. 3;

[0025]FIG. 5 is a sectional view enlarging the same essential portion of the tape taken along a line B-B of FIG. 3;

[0026]FIG. 6 is a plane view of a portion of the tape having a hole enlarged in an elliptic shape;

[0027]FIG. 7 is a sectional view enlarging an essential portion of the tape taken along a line B-B of FIG. 6;

[0028]FIG. 8 is a partially sectional vertical view of a porous pipe showing other embodiment of the invention;

[0029]FIG. 9 is a sectional view enlarging an essential portion of a pipe showing other embodiment of the invention;

[0030]FIG. 10 is a sectional view enlarging an essential portion of a pipe showing other embodiment of the invention;

[0031]FIG. 11 is a sectional view enlarging an essential portion of a pipe showing still other embodiment of the invention; and

[0032]FIG. 12 is a sectional view enlarging an essential portion of a pipe showing still other embodiment of the invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

[0033] An explanation will be given of an embodiment as follows when the invention is embodied in a spiral corrugated pipe. FIG. 1 shows an example of a spiral corrugated pipe 1 provided in accordance with the invention and is formed by spirally winding a single piece of a resin made tape 2. As a material of the resin made tape 2, there are conceivable various kinds thereof such as polyethylene resin, vinyl chloride resin and the like.

[0034] A resin made tape 2 is constituted by a corrugated shape having a channel-like section comprising a center piece 3 and a pair of side pieces 4, 4 integrally provided at both ends of the center piece 3 in a direction of crossing the center piece 3 in orthogonal outer directions. A pair of connection pieces 5, 5 projected orthogonally in outer directions are integrally provided at front ends in the width direction of the respective side pieces 4, 4 along a longitudinal direction. Further, the center piece 3 is formed with a number of holes 6, 6 . . . in one row along the longitudinal direction. The holes 6, 6 . . . can also be formed in two or more rows.

[0035] By spirally winding the resin made tape 2 comprising the above-described constitution such that the center piece 3 is disposed on an inner side in the diameter direction, there is formed the spiral corrugated pipe 1 having a corrugation in the longitudinal direction. At that occasion, the connection piece 5 on a side of preceding in the pipe longitudinal direction and the connection piece 5 on a side of succeeding immediately thereafter, are overlapped by each other and melted together or adhered together to thereby integrate each other.

[0036] Although in FIG. 1, the connection pieces 5, 5 are overlapped substantially over total widths thereof, the connection pieces 5, 5 may partially be overlapped in a possible range. Or, it is also possible to interpose other connection tape between the connection pieces 5, 5 and the connection tape and the connection piece 5 is melted together or adhered together without overlapping the connection pieces 5. Or, it is conceivable to melt together or adhere together other connection tape and the side piece 4 without providing the connection piece 5.

[0037] There is provided the corrugated pipe 1 constituted as described above, which is aligned with a number of the holes 6 at a bottom portion of a valley of an outer periphery thereof constituting the tape center piece 3. In this case, the preceding side and the succeeding side of the spiral portion are melted together or adhered together at portions of the connection pieces 5, 5, which are not provided with the holes 6. Therefore, it is not necessary to provide an overlap margin at the center piece 3, the hole 6 can be formed to the full width of the center piece 3, thereby, the porosity can be increased twice or more as much as that of the conventional example. When a representative example is shown, according to the conventional example of FIG. 12, there is provided a constitution having the porosity of only about 5%, according to the constitution of the embodiment, the porosity can be increased to 10% or more.

[0038] Further, as a modified example of the pipe 1 of FIG. 1, it is conceivable to constitute the pipe 1 in which the center piece 3 is wound to constitute an outer side thereof and the holes 6 are provided at a top face of a mountain portion of the outer periphery.

[0039]FIG. 2 shows an outline of a producing apparatus for producing the above-described porous pipe 1. In the drawing, notation 11 designates a tape molding machine for molding the resin made tape 2. Specifically, by extruding a resin in a molten state through a molding die 10, there is continuously molded the tape 2 having a predetermined sectional shape, more specifically, the channel-like section having the connection piece 5.

[0040] Notation 12 designates a pipe forming machine for forming the pipe 1 by spirally winding the tape 2. For example, the pipe forming machine is provided with a rotating mandrel, not illustrated, and the pipe 1 is formed by winding the tape 2 around the mandrel and rotating the mandrel while feeding the tape 2 in an axial direction.

[0041] Further, the tape 2 immediately after having been molded and extruded from the tape molding apparatus 11, is employed to the pipe forming machine 12, thereby, molding of the tape 2 and forming of the pipe 1 are continuously carried out.

[0042] In continuously forming the pipe 1, there is arranged a perforating machine 13 for perforating the tape 2 at a stage before forming the pipe between the tape molding machine 11 and the pipe forming machine 12. As the perforating machine 13, there is conceivable, for example, a constitution as shown by the drawing comprising a pair of circumferentially moving endless members 14 and 15 arranged at one face side of the tape 2. There are formed a number of projected portions 16 for making recesses or notches 17 having a predetermined depth or forming holes having a predetermined shape to the surface of the tape 2 at outer peripheral faces of the endless members 14 and 15 at intervals in the circumferential direction.

[0043] According to the constitution of the above-described the perforating machine 13, when the endless members 14 and 15 are circumferentially moved in a moving direction of the tape 2 by pertinent driving means in synchronism therewith, the notches 17, 17 . . . are formed at pitch intervals of the projected portions 16 by combining the two endless members 14 and 15. At this occasion, by retarding peripheral speed of the endless members 14 and 15 relative to winding speed of the pipe forming machine 12, produced by driving force of the pipe forming machine 12 is exerted on the tape 2 between the endless members 14 and 15 and the pipe forming machine 12. The tape 2 is gradually elongated in the longitudinal direction by the tension and therefore, in accordance therewith, the recess or the notch 17 is successively enlarged in the longitudinal direction of the tape to thereby constitute the hole 6 in the predetermined shape. There is shown to enlarge the surface of the tape 2 at a portion designated by a white arrow mark on the upper side of FIG. 2.

[0044] Further, although as shown by the drawing, the hole 6 is gradually inclined skewedly from the reason that the tension exerted on the tape 2 differs between left and right sides, it is conceivable to previously cut the notch 17 inversely skewedly by anticipating the inclination. Or, it is conceivable to prevent the hole 6 from being inclined by pertinently setting the tension.

[0045] At any rate, the shape of the hole 6 is not limited to such a shape but can variously be modified by changing means for forming the notch 17, for example, a shape of the projected portion 16 or the like. Further, the projected portion 16 may be of an edge-like shape, a rod-like shape or the like so far as the above-described recess, notch 17 or the hole can be formed.

[0046] Further, as described later, as a result of the elongation, surrounding of the hole 6 is gradually thin-walled and the pipe wall at the surrounding of the hole 6 becomes a shape which is most preferable for the absorbing and draining function.

[0047] The driving force of the endless members 14 and 15 can be outputted from the side of the pipe forming machine 12, further, normally, the peripheral speed of the endless members 14 and 15 may be lower than the winding speed of the pipe forming machine 12.

[0048] It is not necessarily needed that the recess or the notch 17 or the like is pierced to the rear face of the tape 2 as described above. For example, even when the rear face side of the hole is closed, the hole is opened by the above-described elongation and becomes the hole 6 pierced to the rear face. Naturally, it is conceivable that the hole 6 pierced to the rear face is formed by the endless members 14 and 15 from the start and the hole is enlarged in the longitudinal direction to constitute a predetermined shape by the above-described pulling operation. Or, it is also conceivable that the hole 6 having a predetermined shape is formed from the start and the hole 6 is pulled to a degree of not being crushed or deformed by the viscoelasticity of the tape 2 near to a molten state yet.

[0049] Further, the pitch of forming the holes 6 can be changed by changing the interval between the projected portions 16, 16. Or, by forming the projected portion 16 only at portions of circumferences of the endless members 14 and 15, the holes 6 can be provided only at portions in the circumferential direction of the pipe 1.

[0050] Further, means for forming the recess or the notch 17 or the hole 6 is not limited to the above-described but, for example, the means can be a punch or the like reciprocating relative to the face of the tape 2.

[0051]FIG. 3 enlarges a portion of the hole 6 at a surface of the tape 2 formed as described above. According to the embodiment, the substantially rectangular hole 6 is constituted and as described above, the hole 6 is inclined slightly in the longitudinal direction of the tape from the reason that the tension exerted from the pipe forming machine 12 to the tape 2 differs between the left side and the right side. FIG. 4 is a view enlarging a section taken along a line A-A of FIG. 3 constituting a width direction of the tape and FIG. 5 is a view enlarging a section taken along a line B-B of FIG. 3 constituting the longitudinal direction of the tape. As is understood by the drawings, in the width direction, the inner peripheral face of the tape 6 is constituted by an arc-like shape slightly buldged forward the center of the tape 6 in the thickness direction. On the other hand, in the longitudinal direction, the wall thickness at the surrounding of the hole 6 is gradually thinned toward the inner peripheral face of the hole 6, thereby, the surface 18 at the surrounding of the hole 6 is gradually inclined while drawing an arc.

[0052]FIG. 6 is an enlarged view of a portion of the hole 6 when the hole 6 in an elliptical shape is formed and FIG. 7 is a view enlarging a section taken along a line A-A of FIG. 6. As shown by the drawing, in the case of elliptical shape, the wall thickness of the surrounding the hole 6 is gradually thinned toward the inner peripheral face of the hole 6 over the total periphery of the hole 6 and a surface 18 of the surrounding of the hole is gradually inclined while drawing an arc. Such a gradual inclination can be controlled by pertinently setting the shape of the hole 6 and the tension from the side of the pipe forming machine 12.

[0053]FIG. 8 shows other embodiment of the invention. According to the embodiment, in the spiral corrugated pipe 1 the same as that of FIG. 1, the holes 6 are formed not only at the center piece 3 at the recessed bottom portion of the outer periphery but also at the side piece 4 constituting the side wall of the recessed portion and the top portion of the mountain portion.

[0054] Particularly, according to the embodiment, the hole is formed at the stage of the tape 2 before forming the pipe as described above and therefore, the hole 6 can easily be formed at the portion of the side piece 4. Further, according to the embodiment, the top portions of the mountain portions are portions for melting together or adhering together, particularly, in the case of melting together the portions, when the hole is formed by a drill or the like after the portions are melted together as in the conventional example, there is a concern that the strength is reduced by causing residual stress. However, according to the invention, the hole is formed in a state before melting together the portions near to a molten state and therefore, the residual stress is not caused and the strength is not reduced. Therefore, the holes 6 can be formed substantially over the total face in the longitudinal direction of the pipe.

[0055]FIG. 9 and the drawings successive thereto show other embodiments of the porous pipe 1 embodied according to the invention. In FIG. 9, the hole 6 is formed at the flat tape 2 in place of the tape 2 having the channel-like section as described above. The flat tape 2 is spirally wound similar to the above-described and in the winding operation, a preceding side of an end edge of a spiral portion and a succeeding side of an end edge of a spiral portion are overlapped each other and melted together or adhered together. Further, an outer periphery of the pipe 1 formed by the flat tape 2, is wound with other outer side tape 20 having a channel-like section and having lips 19 at both ends thereof in the width direction while melting or adhering the lips 19 together with an outer peripheral face of the pipe 1 such that a portion of a channel-like groove is directed inwardly to thereby constitute a reinforcement. At this occasion, the flat tape 2 is wound by a pitch larger than the width of the outer side tape 20 such that the hole 6 of the pipe 1 is not closed by the outer side tape 20.

[0056]FIG. 10 shows a composite pipe comprising the porous pipe 1 of the invention comprising the flat tape 2 and the outer side tape 20 having the channel-like section similar to FIG. 9. According to the composite pipe, a hole 21 is also formed at a top portion of a mountain portion of the outer side tape 20 and the hole 6 of the porous pipe 1 on the inner side and the hole of the outer side tape 20, are communicated to each other via the groove portion of the outer side tape 20. In the outer side tape 20, the lip 19 is melted or adhered to the outer peripheral face of the porous pipe 1 on the inner side, at the same time, an end face of the lip 19 is skewedly cut and in the winding operation, a preceding side of the lip and a succeeding side of the lip are melted together or adhered together. Further, the holes 21 of the outer side tape 20 may be formed at a side piece 22 in place of the top portion or may be formed at both of the top portion and the side piece.

[0057] A pipe of FIG. 11 is constituted by winding the outer side tape 20 having the channel-like section on an outer side of the porous pipe 1 of the invention similarly comprising the flat tape 2. Further, the outer side tape 20 is melted or adhered together with the outer peripheral face of the porous pipe 1 on the inner side at the top faces of the mountain portions such that the channel-like groove portion is disposed on the outer side. In this case, according to the outer side tape 20, heights of the left and right side pieces 22, 22 of the channel-like shape, differ from each other. Therefore, when a preceding side of a tongue piece 19 and a succeeding side of the tongue piece 19 are overlapped in the winding operation, a gap 23 is formed between the tongue pieces 19, 19 and the gap 23 is communicated to the hole 6 of the porous pipe 1 on the inner side by passing through the channel-like groove portion.

[0058] Either of the above-described embodiments of FIG. 10 and FIG. 11, is constructed by a structure in which a path from outside to the hole 6 of the porous pipe 1 on the inner side, is complicated by the outer side tape 20 and sediments are less clogged than a pipe having a simple one-layered structure. The outer side tapes 20 of FIG. 10 and FIG. 11 can be perforated by the method of FIG. 2.

[0059] In FIG. 12, in the case of the porous pipe 1 of the invention similarly comprising the flat tape 2, similar to the above-described, in the winding operation, a preceding side of an end edge of a spiral portion and a succeeding side of an end edge of a spiral portion are overlapped to each other and melted together or adhered together and a reinforcement tape 24 having a section in, for example, a mountain shape, is spirally wound along the overlapped portion. The reinforcement tape 24 is constituted by, for example, a tape made of hard resin and integrated to the outer peripheral face of the pipe 1 by melting or adhering a rear face thereof thereto.

[0060] The invention is not limited to the above-described embodiments but can variously be modified within the scope of claims, described below and includes the various modifications. 

What is claimed is:
 1. A porous pipe, wherein a wall thickness at a surrounding portion of the hole in the circumferential direction is partially or wholly formed gradually thin-walled toward an inner peripheral face of the hole, so as to make the surface of the surrounding portion inclined.
 2. A porous pipe, comprising a number of holes piercing the pipe wall thereof and constituted by spirally winding a tape, wherein said holes are formed in such a manner as that recess, notch, or hole that are made immediately after tape molding is formed into the predetermined shape by elongating the tape.
 3. The porous pipe according to claim 2, wherein the tape is elongated by a driving force of a pipe forming machine for spirally winding the tape.
 4. A porous pipe, which is constituted by spirally winding a tape with a channel-like section, wherein a hole is formed at a center piece portion in the channel-like shape and said porous pipe is constituted by melting together or adhering together a preceding tape and a succeeding tape in a longitudinal direction of the pipe on an outer side of a side piece on an outer side of the center piece portion.
 5. The porous pipe according to anyone of claims 1 through 4, wherein said porous pipe is a spiral corrugated pipe having a number of recesses and projections in an axial direction of the pipe and a number of holes are formed at a valley portion of an outer periphery thereof.
 6. The porous pipe according to claim 5, wherein the hole is formed also at a side wall of the valley portion and/or a top portion of a mountain portion of the outer periphery of the pipe.
 7. The porous pipe according to any one of claims 1 through 3, wherein said porous pipe is a pipe constituted by spirally winding a flat tape and the flat tape is formed with a number of holes.
 8. The porous pipe according to claim 7, further comprising other spirally wound tape or an outer pipe spirally wound with other tape on an outer side of the porous pipe.
 9. An apparatus of producing a porous pipe, constituted such that a tape molded by tape molding portion is directly employed to a pipe forming portion for forming a pipe by spirally winding the tape, so as to successively mold the tape and then to form the pipe and that it is between the tape molding portion and the pipe forming portion that a hole forming portion to provide a recess or a notch with a predetermined depth at a surface of the tape or a hole with a predetermined size is arranged.
 10. The apparatus of producing a porous pipe according to claim 9, wherein the recess or the notch or the hole formed by the hole forming portion is formed into a hole having a predetermined shape by an elongation from a side of the pipe forming portion.
 11. The apparatus of producing a porous pipe according to claim 10, wherein the tape is elongated by a driving force of the pipe forming portion.
 12. A method of producing a porous pipe, constituted in such a manner as that a tape molded by tape molding portion is directly employed to a pipe forming portion for forming a pipe by spirally winding the tape, to thereby carry out successively molding the tape and then forming the pipe, wherein a recess or a notch with a predetermined depth is formed or a hole is formed at a surface of the tape and then a hole with a predetermined shape and a predetermined size is formed by elongating said recess, notch or hole from a side of the pipe forming portion, while the tape is conveyed from the tape molding portion to the pipe forming portion.
 13. The method of forming a porous pipe according to claim 12, wherein the tape is elongated by a driving force of the pipe forming portion. 